- 430 antiquities in Scotland. May 30. 
where these structures abound, to give a very prow 
bable account of the manner in which this art hag 
been originally discovered, and of the causes'that have 
-occasioned the knowledge of it to be lost, even in the 
‘cquntries where it was once universally practised. 
Through ali the northern parts of Scotland, a par- 
‘ticular kind of earthy iron ore, of a very -vitrescible 
nature, much abounds. This ore might have been 
accidentally mixed with some stones at a place where 
-a great fire was kindled ; .and being fused by the heat, 
would cement the stones-into oné solid mafs, and give 
‘the first hint of the uses'to which it might be applied. 
A few experiments would satisfy them of the pofsi- 
bility of executing at large what had been acciden- 
tally discovered in miriature. 
This knowledge being thus attained, nothing seems 
to be more-simple and natural than its application to 
the formation of:the walls of their fortified places. 
‘Having made choice of a proper place for their 
fort, they would rear a wall all round:the area, build- 
ing the outside of it as firm as they could of dry 
stones piled one above another, the interstices be- 
tween-them being filled full of this vitrescible iron 
ore; and the whole supported by a backing of loose 
stones piled carelefsly behind it. 
’ When the wall was thus far completed, with its 
‘facing all round reared to the height they wifhed for, 
nothing more was necefsary-to give it the entire fi- 
-nifhing but to kindle a-fire, all round it, sufficiently 
jntense to melt the vitrescible ore, and thus to ces 
ment the whole into one coherent mafs, as far as the 
influence of that heat extended. As the country then 
